Sorry, missed this thread before. I hope you won't mind if I jump in at this late stage.

Specifically, recovery weeks. This is all about intensity. When I am touring I can ride six days a week, fifty or sixty miles a day, for eight weeks at a time. Probably more, maybe indefinitely, but eight weeks is my longest tour so far. Fatigue rarely becomes an issue except following a big climbing day, and is sorted out by taking an easy day or a day off, because when touring almost all the rest of my riding is in z1 and z2, and I can recover adequately overnight.

But when I was training for racing I absolutely needed to take the easy recovery weeks, whether I felt I needed them or not. In fact, I needed to take one every third week, not every fourth, because being in my late fifties I couldn't handle the 3:1 cycle. I discovered this the hard way, by trying to get fit quick after injury using Carmichael's time-crunched training program. It worked, after a fashion, but as well as making me faster it burned me out. After a couple of months of it I found I couldn't train properly for several weeks, because the accumulated fatigue was preventing me from hitting the numbers, completing my usual intervals etc. I stopped getting fitter, and just got exhausted instead. I'd strongly advise against that, it gets into your head and in the end you actively dislike the thought of getting on the bike.

So I'd err on the side of caution. If your regular weeks contain a significant amount of intensity - intervals, or a couple of hard days in the hills, or whatever - then I would definitely recommend that you make every fourth week an easier week. It will keep you fresh, and you will actually progress faster, over a much longer period, than if you try to maintain the intensity week-in, week-out. And it's supposed to be fun, right? Overreaching, followed by overtraining, is not fun, it's depressing.